Gorden bars, cover plates and an AirJet chaffer will fix the problems you are having. You're welcome to phone me at 1-800-745-1680 or cell 1-800-745-1681 for a complete consultation.
Chaff is an indication of low fan speed or seives to open and white caps is to do with threshing.Have the fan up full then try closing the bottom seive a little at a time till you get a better sample. Also keep front portion of chaffer closed.Also try running your rotor up a touch and close the concave right up.